Redo GN "args" command

Redo GN "args" command

Previously "gn args" printed build arguments. That has now moved to "gn args <outdir> --list" along with a new --short mode that's a bit more convenient for some uses.

Now "gn args" runs your editor on the build arguments for the given output directory, and re-generates the build given those arguments. This is an easier way to manage changing build arguments for a build (previously you would have to re-type everything or edit build.ninja manually).

"gn gen" now always uses the existing arguments for the given output dir, unless "--args" is manually specified (giving the old behavior of just using those). This also allows a more convenient way for a user to recover from a borked build (sincetimes I ran into a state where something was missing that prevent ninja from even starting enough to rebuild the build).

I removed the "show" and "refresh" ninja phony rules since the new commands cover those cases.

This patch adds some additional tracing to build startup since I noticed it was missing when trying to figure out why the args command was so slow (I fixed the main reason, it was with new code I added).

Added proper escaping for printing string values and unit tests for these.

Two minor build file fixes.

R=scottmg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=268042

[tfarina, 2014-05-01 18:06:46]

https://codereview.chromium.org/265693003/diff/60001/tools/gn/args.cc
File tools/gn/args.cc (right):

https://codereview.chromium.org/265693003/diff/60001/tools/gn/args.cc#newcode31
tools/gn/args.cc:31: "  directory will be used (this is in the file gn.args in
the build\n"
so does that mean the sequence of commands you be like this?

$ gn args out/Release_gn
# editor opens
# type is_debug=false
# type use_aura=true

$ gn gen out/Release_gn

if I understood this right, it seems cool, because it saves typing and time in
the subsequent calls to gn gen.

[brettw, 2014-05-01 18:19:48]

On 2014/05/01 18:06:46, tfarina wrote:
> https://codereview.chromium.org/265693003/diff/60001/tools/gn/args.cc
> File tools/gn/args.cc (right):
> 
>
https://codereview.chromium.org/265693003/diff/60001/tools/gn/args.cc#newcode31
> tools/gn/args.cc:31: "  directory will be used (this is in the file gn.args in
> the build\n"
> so does that mean the sequence of commands you be like this?
> 
> $ gn args out/Release_gn
> # editor opens
> # type is_debug=false
> # type use_aura=true
> 
> $ gn gen out/Release_gn

This step is implicit, you only need to run "args" and then ninja, but otherwise
that looks right.

[scottmg, 2014-05-01 19:25:02]

I don't really love it trying to learn how to launch my editor, but I guess it's
convenient?

lgtm

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc
File tools/gn/command_args.cc (right):

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc...
tools/gn/command_args.cc:182: return;
This should probably exit(1) instead otherwise the subsequent gen will be
confusing.

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc...
tools/gn/command_args.cc:236: // Windows they can come out as forward slashes
here, and that conuses some
confuses

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc...
tools/gn/command_args.cc:242: std::string argfile_default_contents =
It'd be nice to have the default values/comments in the generated file,
commented out (i.e. roughly what "gn args" looks like now). Is that possible?

https://codereview.chromium.org/265693003/diff/30011/tools/gn/setup.cc
File tools/gn/setup.cc (right):

https://codereview.chromium.org/265693003/diff/30011/tools/gn/setup.cc#newcod...
tools/gn/setup.cc:137: const char CommonSetup::kBuildArgFileName[] = "gn.args";
Should it be .gn extension so that a syntax highlighting editor could pick up
some settings?

[brettw, 2014-05-01 19:46:54]

Yeah, the editor stuff is kind of annoying but I think the convenience factor
with this is very high, especially for some users who have lots of flags and are
frequently tweaking them.

I added outputs for the filename the command is editing so its more obvious this
is a shortcut and to make it clear how you would do it manually if your editor
is having problems.

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc
File tools/gn/command_args.cc (right):

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc...
tools/gn/command_args.cc:182: return;
I added proper error checking and return values to these functions.

https://codereview.chromium.org/265693003/diff/30011/tools/gn/command_args.cc...
tools/gn/command_args.cc:242: std::string argfile_default_contents =
There will be many many dozens of arguments, so I'm not sure this will look that
useful. I'm also wary that this will encourage people to try setting different
options when generally they should leave it alone.

https://codereview.chromium.org/265693003/diff/30011/tools/gn/setup.cc
File tools/gn/setup.cc (right):

https://codereview.chromium.org/265693003/diff/30011/tools/gn/setup.cc#newcod...
tools/gn/setup.cc:137: const char CommonSetup::kBuildArgFileName[] = "gn.args";
Good idea, I renamed it args.gn

[brettw, 2014-05-03 04:32:25]

Committed patchset #7 manually as r268042 (presubmit successful).

[tfarina, 2014-05-03 04:38:24]

https://codereview.chromium.org/265693003/diff/170001/tools/gn/BUILD.gn
File tools/gn/BUILD.gn (right):

https://codereview.chromium.org/265693003/diff/170001/tools/gn/BUILD.gn#newco...
tools/gn/BUILD.gn:206: "value_unittest.cc",
miss 'git add tools/gn/value_unittest.cc'?

g++: error: ../../tools/gn/value_unittest.cc: No such file or directory

[tfarina, 2014-05-03 04:56:55]

https://codereview.chromium.org/265693003/diff/170001/tools/gn/command_args.cc
File tools/gn/command_args.cc (right):

https://codereview.chromium.org/265693003/diff/170001/tools/gn/command_args.c...
tools/gn/command_args.cc:222: return system(cmd.c_str()) == 0;
and the fix for this? the return type is void rather than bool. The bot was
complaining about this too: 

../../tools/gn/command_args.cc:222:33: error: return-statement with a value, in
function returning 'void' [-fpermissive]